(Table 1) Different age analysis from sediment cores XP98-PC-4 and XP98-PC-2

Sea-surface temperatures (SSTs) in the Sea of Okhotsk were reconstructed based on alkenone unsaturation indices in two sediment cores. Alkenone-SSTs were found to range from 3 to 9 °C over the last 85 kyr with higher SST values in warm periods: Holocene and the oxygen isotope stage (OIS) 5a. In the last glacial periods (OIS 4 and 3), average alkenone SST was estimated to be 4 °C, which was 4 °C lower than the Holocene on average. However, alkenone SSTs around the last glacial maximum (LGM) are as high as those of the Holocene. The variation patterns of U37K' in the Okhotsk Sea were found to be similar to those reported in the Sea of Japan [Org. Chem. 32 (2001) 57] over the last 30 kyr, although the SSTs were lower in the Sea of Okhotsk. The higher U37K' values around the LGM may be a rather common phenomenon in semi-closed marginal seas such as the Japan Sea and the Okhotsk Sea, which are both adjacent to the northwestern Pacific. Such an anomaly in the LGM may have been caused by either a seasonal shift of coccolith blooming or a contribution from a different strain or species that produces alkenones本研究基于两块沉积岩芯（sediment cores）中的烯酮不饱和度指数（alkenone unsaturation indices），重建了鄂霍次克海的海表温度（Sea-surface temperatures, SSTs）记录。研究发现，过去85 kyr内，鄂霍次克海的烯酮海表温度（alkenone-SSTs）介于3~9℃之间，在温暖时期即全新世（Holocene）与氧同位素阶段（oxygen isotope stage, OIS）5a中，海表温度更高。在末次冰期（last glacial periods，对应OIS 4与3）阶段，烯酮海表温度的平均估值约为4℃，较全新世平均水平低4℃。不过，末次冰盛期（last glacial maximum, LGM）前后的烯酮海表温度可达到与全新世相当的水平。尽管鄂霍次克海的海表温度整体低于日本海，但过去30 kyr以来，该海域U37K'的变化模式与日本海已报道的结果[Org. Chem. 32 (2001) 57]较为相似。末次冰盛期前后较高的U37K'值，可能是西北太平洋毗邻的半封闭边缘海（如日本海与鄂霍次克海）较为普遍的现象。该末次冰盛期的异常现象，可能由颗石藻水华（coccolith blooming）的季节偏移，或是产生烯酮的不同菌株或物种（strain or species）的贡献所导致。